Also Known As
Dog Fennel, Stinkweed
Mayweed Chamomile, Anthemis cotula L., is native to the Mediterranean region, but has been widely introduced as a weed in the temperate zones. In 1995, it could be found in almost all of the lower 48 states.
Mayweed is an annual bushy, ill-scented herb; however, mayweed is highly attractive to ladybird beetles that feed on aphids. The plant grows from ½ to 2 feet tall. Mayweed can be found in flower from May to September but the main flowering period is June to July. The flowers are white, commonly 12, and up to ½ inch long.The flowers are pollinated by insects, mainly flies. Mayweed chamomile is potentially allelopathic to certain forage species.
Photo by Rusty Russell at USDA-NRCS PLANTS Database
Mayweed chamomile reproduces by seeds. Plants of average size are capable of producing from 5000 to 17,000 seeds. This plant is a weed of disturbed soils and may be an indicated of loamy soils. Seeds germinate mainly in the autumn and spring, but some germination can occur throughout the year. Seeds can remain over 50% viable in the soil for more than 11 years.
Mayweed chamomile is frost-hardy at the rosette stage and may grow as a winter annual. It is moderately drought-resistant, and summer drought may restrict the size of the plant, but does not prevent seed development. Once the mayweed becomes established, eradication is impossible. Mayweed chamomile is a serious problem in cereal crops, waste areas, pastures, and along roadsides. Contact with mayweed can cause skin rashes and irritation to the mucous membranes of livestock.
Combinations of rotation grazing and herbicides treatments are the best methods of successful control of mayweed chamomile in pastures.
It is most important to prevent the production and spread of mayweed chamomile seed. Seed is dispersed by water in ditches and streams, in contaminated crop seed, and by animals or equipment. Prevent seed production whenever possible; sow clean seed, manage animal movement to avoid infested areas, and clean equipment whenever it is moved from infested to uninfested areas. Agricultural seed, hay, and livestock feeds may become contaminated with mayweed chamomile seed. Always select and use certified weed-free forage, feed, and seed to prevent reinfestation of an area. Quarantine livestock known to have been in areas infested with mayweed chamomile. It may be necessary to clean the animals’ coats before they are moved to un-infested land.
Photo by R. A. Howard at USDA-NRCS PLANTS Database
Mechanical Control: Small infestations can be eliminated by hand pulling and digging, but this is not practical for large infestations. Hand pulling mayweed chamomile before it goes to seed will prevent new infestations. Cultivation is most successful if done when the plant is in the seedling stage, prior to seed set. Cultivation should be performed as often as necessary to control this weed. Mowing mayweed chamomile is not effective. If mowed too early, the plant grows more prostrate and can produce flowers below the height of a mower blade.
Biological Control: There are currently no biological control methods available for mayweed chamomile. Manage livestock grazing to improve the competition of desirable grasses and legumes and avoid overgrazing of plants.
Chemical Control: There are several herbicides available to provide control of mayweed chamomile. In grasses grown for seed, the herbicides bromoxynil (Buctril®) and dicambda (Clarity®) can be applied and should provide fair to good control. In small grain crops, many herbicides can be used, although control varies. Mayweed chamomile is resistant to a number of herbicides, especially Group II herbicides. Repeated herbicide applications may be needed to achieve control of an infestation.